Valhi Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income Loss [Line Items]
Marketable securities, Balance at beginning of year	$ 1.6	$ 2.8	$ 2.1
Marketable securities, Unrealized losses arising during the year		(1.0)
Marketable securities, Less reclassification adjustments for amounts included in realized loss (gain)		(0.2)	0.7
Marketable securities, Balance at end of year	1.6	1.6	2.8
Currency translation, Balance at beginning of year	(22.6)	59.2	53.3
Currency translation, arising during the year	(55.5)	(81.8)	5.9
Currency translation, Balance at end of year	(78.1)	(22.6)	59.2
Balance at beginning of year	(148.6)	(8.0)	(42.0)
Other comprehensive income (loss)	(48.4)	(140.6)	34.0
Balance at end of year	(197.0)	(148.6)	(8.0)
Interest Rate Swap
Accumulated Other Comprehensive Income Loss [Line Items]
Unrealized losses during the year	(1.7)
Less reclassification adjustments for amounts included in interest expense	0.4
Balance at end of year	(1.3)
Defined Benefit Pension Plans
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of year	(132.0)	(76.5)	(101.5)
Amortization of prior service cost and net losses included in net periodic pension cost	6.7	6.3	8.4
Net actuarial gain (loss) arising during the year	2.3	(61.7)	12.6
Plan curtailment		(0.1)	4.0
Balance at end of year	(123.0)	(132.0)	(76.5)
OPEB
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of year	4.4	6.5	4.1
Amortization of prior service cost and net losses included in net periodic pension cost	(1.0)	(1.3)	(1.4)
Net actuarial gain (loss) arising during the year	0.4	(0.8)	1.3
Plan amendment			2.5
Balance at end of year	$ 3.8	$ 4.4	$ 6.5